Methods and systems for transmission of group-specific media streams over a distribution network are adequately known. In these prior art methods, various media streams are fed into one point or multiple predetermined points in the distribution network, and at the other end of the distribution network are specifically delivered to individual subscribers or groups of subscribers through what are known as multicast replication points.
An important consideration in such multimedia communication systems is providing means that make it possible to switch from one program channel to another program channel. In this context, when switching between two program channels the problem frequently arises that visible interference in the displayed content is noticeable to the subscriber. When switching between channels at an arbitrary point in time, it is not guaranteed that a seamless transmission of the target channel or immediate playback of the target channel will be possible at the subscriber. When switching from a program currently being displayed to a new program, it is always necessary to ensure that a complete frame is transmitted when starting to display the new program, so that continuous, seamless frame construction is made possible following the switchover process, this making it possible to avoid visible interference at the subscriber.
A prior art method for seamless switchover between program channels in a digital video-based entertainment network is described in, for example, U.S. Published Application No. 2004/0034864 A1. Described therein is a system for transmitting digital video signals, which has a head end including an encoder, a device for detecting and evaluating channel-change messages, and a device for creating complete frames. The head end is connected to a subscriber-side terminal through a distribution network. A subscriber initiates a channel change by entering, at his terminal, a corresponding channel-change command that is transmitted through the distribution network to the head end. Based on the evaluation of the channel-change message, the detection device of the head end causes the encoder to generate an I-frame, which is to say a complete frame of the new target channel. The complete frame of the new target channel is then transmitted to the subscriber's terminal. In other words, the actual switchover between program channels takes place in the encoder of the head end.